This invention relates to a dynamic RAM (random access memory) and a special mode control method therefor, and more particularly to effective technologies used for dynamic RAM provided with a low power consumption mode intended only for information retention operation.
The dynamic RAM operation modes include normal write/read, test, and refresh modes. To lower power consumption of a memory system with dynamic RAM, low power consumption modes such as a battery backup mode have been proposed; such a battery backup mode is reported, for example, on Technical Bulletin ED-90-78 of Institute of Electronics and Communication Engineers of Japan. The battery backup mode is set by fixing CASB signal low and RASB signal high over 16 ms or more after automatic refresh is started with the CBR (CASB before RASB) mode.